One of the key advantages of single-pole (SP) head/media, with a magnetically soft underlayer (SUL) and a perpendicular recording system, is the capability to provide a larger write field (than that of a ring head) to enable writing into the relatively thick media with high anisotropy constant. The latter quality leads one to assume better thermal stability associated with perpendicular recording.
FIG. 1 is a schematic representation of a typical single pole vertical recording system of the prior art. Seen there is single write pole 13 whose ABS (air bearing surface) moves parallel, and close to, the surface of recording medium 16. The latter comprises an upper, high coercivity, layer (not shown) on a magnetically soft underlayer. Coils 12 generate magnetic flux in yoke 11 which passes through main pole 14 into tip 13 and then into media 16 (where a bit is written). The magnetic circuit is completed by flux that passes through the soft under layer and then back into return pole 11. The space enclosed by the yoke and poles is normally filled with insulating material 17.
The traditional single pole perpendicular writer with soft underlayer has two major problems—insufficient field gradient in the down track direction and adjacent track erasure (ATE) caused by side fringing fields. The second problem becomes even more severe when the neck height of the single pole is reduced so as to increase the write field, i.e. overwrite (OW) capability.
A shielded pole perpendicular writer has been proposed to improve field gradient and to reduce ATE [1]. Unfortunately, the presence of shields also reduces the perpendicular field component so a shielded pole head will generate insufficient write field, even taking into consideration the increased in-plane field. Proper design of a shield pole head should take both ATE improvement and OW performance into consideration.
A routine search of the prior art was performed with the following references of interest being found:
A tapered pole is described in U.S. Pat. No. 5,173,821 while Inamura describes a tapered pole portion at the tip in U.S. Pat. No. 5,995,343. In U.S. Pat. No. 5,600,519, Heim et al teach the use of a tapered pole tip to increase the head field and, in U.S. Pat. No. 4,935,832, Das et al. show side shields around the write pole.